I'm not sure how close of friends you need to be to qualify, but if you belong to a resort or club, you likely have more than 10 if you spend any amount of time there!

As far as close friends, I have between 8-15 that we do nude stuff with on some fairly frequent basis. From travelling to hotsprings, to going over to their house and sitting in their hottub, to camping/hiking stuff, I'm actually surprised at how many people I do know that I socialize with that I've done nekkid stuff with.
I recently found out that my best friend and his wife (who I never ever did anything socially nude with previously), acutally went to a spa and hung out nude. I've been running around Washington and Oregon for 4 years now, and they'd always been a part of my non nudist life, but never more than hang out friends. The one day about 6 months ago, we all went and sat in their hottub nude, and had a discussion about how much they actually did. I was shocked and surprised!
I was thrilled to add a close buddy and his wife to my growing list of 30 somethings in the area who get together for small private events! It is exciting to know there is more folks out there than we think, and given the right circumstances are willing to do low key things nekkid, provided they are kept quiet from the greater world.